﻿/*
Copyright (c) 2010 <a href="http://www.gutgames.com">James Craig</a>

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.*/
 
#region Usings

using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;

#endregion

namespace sBlog.Net.Domain.Utilities
{
    /// <summary>
    /// Utility class that handles encryption
    /// </summary>
    public static class AESEncryption
    {
        #region Static Functions
 
        /// <summary>
        /// Encrypts a string
        /// </summary>
        /// <param name="PlainText">Text to be encrypted</param>
        /// <param name="Password">Password to encrypt with</param>
        /// <param name="Salt">Salt to encrypt with</param>
        /// <param name="HashAlgorithm">Can be either SHA1 or MD5</param>
        /// <param name="PasswordIterations">Number of iterations to do</param>
        /// <param name="InitialVector">Needs to be 16 ASCII characters long</param>
        /// <param name="KeySize">Can be 128, 192, or 256</param>
        /// <returns>An encrypted string</returns>
        public static string Encrypt(string PlainText, string Password,
            string Salt = "Kosher", string HashAlgorithm = "SHA1",
            int PasswordIterations = 2, string InitialVector = "OFRna73m*aze01xY",
            int KeySize = 256)
        {
            if (string.IsNullOrEmpty(PlainText))
                return "";
            byte[] InitialVectorBytes = Encoding.ASCII.GetBytes(InitialVector);
            byte[] SaltValueBytes = Encoding.ASCII.GetBytes(Salt);
            byte[] PlainTextBytes = Encoding.UTF8.GetBytes(PlainText);
            PasswordDeriveBytes DerivedPassword = new PasswordDeriveBytes(Password, SaltValueBytes, HashAlgorithm, PasswordIterations);
            byte[] KeyBytes = DerivedPassword.GetBytes(KeySize / 8);
            RijndaelManaged SymmetricKey = new RijndaelManaged();
            SymmetricKey.Mode = CipherMode.CBC;
            byte[] CipherTextBytes = null;
            using (ICryptoTransform Encryptor = SymmetricKey.CreateEncryptor(KeyBytes, InitialVectorBytes))
            {
                using (MemoryStream MemStream = new MemoryStream())
                {
                    using (CryptoStream CryptoStream = new CryptoStream(MemStream, Encryptor, CryptoStreamMode.Write))
                    {
                        CryptoStream.Write(PlainTextBytes, 0, PlainTextBytes.Length);
                        CryptoStream.FlushFinalBlock();
                        CipherTextBytes = MemStream.ToArray();
                        MemStream.Close();
                        CryptoStream.Close();
                    }
                }
            }
            SymmetricKey.Clear();
            return Convert.ToBase64String(CipherTextBytes);
        }
 
        /// <summary>
        /// Decrypts a string
        /// </summary>
        /// <param name="CipherText">Text to be decrypted</param>
        /// <param name="Password">Password to decrypt with</param>
        /// <param name="Salt">Salt to decrypt with</param>
        /// <param name="HashAlgorithm">Can be either SHA1 or MD5</param>
        /// <param name="PasswordIterations">Number of iterations to do</param>
        /// <param name="InitialVector">Needs to be 16 ASCII characters long</param>
        /// <param name="KeySize">Can be 128, 192, or 256</param>
        /// <returns>A decrypted string</returns>
        public static string Decrypt(string CipherText, string Password,
            string Salt = "Kosher", string HashAlgorithm = "SHA1",
            int PasswordIterations = 2, string InitialVector = "OFRna73m*aze01xY",
            int KeySize = 256)
        {
            if (string.IsNullOrEmpty(CipherText))
                return "";
            byte[] InitialVectorBytes = Encoding.ASCII.GetBytes(InitialVector);
            byte[] SaltValueBytes = Encoding.ASCII.GetBytes(Salt);
            byte[] CipherTextBytes = Convert.FromBase64String(CipherText);
            PasswordDeriveBytes DerivedPassword = new PasswordDeriveBytes(Password, SaltValueBytes, HashAlgorithm, PasswordIterations);
            byte[] KeyBytes = DerivedPassword.GetBytes(KeySize / 8);
            RijndaelManaged SymmetricKey = new RijndaelManaged();
            SymmetricKey.Mode = CipherMode.CBC;
            byte[] PlainTextBytes = new byte[CipherTextBytes.Length];
            int ByteCount = 0;
            using (ICryptoTransform Decryptor = SymmetricKey.CreateDecryptor(KeyBytes, InitialVectorBytes))
            {
                using (MemoryStream MemStream = new MemoryStream(CipherTextBytes))
                {
                    using (CryptoStream CryptoStream = new CryptoStream(MemStream, Decryptor, CryptoStreamMode.Read))
                    {
 
                        ByteCount = CryptoStream.Read(PlainTextBytes, 0, PlainTextBytes.Length);
                        MemStream.Close();
                        CryptoStream.Close();
                    }
                }
            }
            SymmetricKey.Clear();
            return Encoding.UTF8.GetString(PlainTextBytes, 0, ByteCount);
        }
 
        #endregion
    }
}
